GB2320767A - Four group zoom lens system - Google Patents
Four group zoom lens system Download PDFInfo
- Publication number
- GB2320767A GB2320767A GB9726466A GB9726466A GB2320767A GB 2320767 A GB2320767 A GB 2320767A GB 9726466 A GB9726466 A GB 9726466A GB 9726466 A GB9726466 A GB 9726466A GB 2320767 A GB2320767 A GB 2320767A
- Authority
- GB
- United Kingdom
- Prior art keywords
- lens group
- lens
- refractive power
- focal length
- zoom lens
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 230000005499 meniscus Effects 0.000 claims description 3
- 230000004075 alteration Effects 0.000 description 11
- 206010010071 Coma Diseases 0.000 description 6
- 230000011514 reflex Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B15/00—Optical objectives with means for varying the magnification
- G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
- G02B15/144—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only
- G02B15/1441—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only the first group being positive
- G02B15/144105—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having four groups only the first group being positive arranged +-+-
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/009—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras having zoom function
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B3/00—Simple or compound lenses
- G02B3/0006—Arrays
- G02B3/0037—Arrays characterized by the distribution or form of lenses
- G02B3/0062—Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B3/00—Simple or compound lenses
- G02B3/0087—Simple or compound lenses with index gradient
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Lenses (AREA)
Abstract
A zoom lens system includes a first lens group 1 of a positive refractive power, having eg two lenses, which moves linearly toward an object for a magnification change; a second lens group 2 of a negative refractive power; a third lens group 3 of a positive refractive power which moves non-linearly toward the object for a magnification change; and a fourth lens group 4 of a negative refractive power which moves linearly toward the object for a magnification change.
Description
ZOOM LENS SYSTEM
BACKGROUND OF THE INVENTION (a) Field of the Invention
The present invention relates to a zoom lens system, more particularly to a zoom lens system for a single lens reflex camera capable of compensating a change of an introversive coma at a telephoto position.
(b) Description of the Related Art
A conventional zoom lens system for a single lens reflex camera includes a first lens group of a positive refractive power which is movable toward an object along an optical axis for a magnification change, a second lens group of a negative refractive power which is fixed, a third lens group of a positive refractive power compensating an image plane when changing a magnification, and a fourth lens group of a negative refractive power which is movable toward an object as the first lens group moves for a magnification change.
However, the conventional zoom lens system with four lens groups has a problem of an introversive coma at a telephoto position, where an off-axis aberration varies greatly because an exit angle of an incident light beam entering the lens at an arbitrary angle changes as the fourth lens group moves.
SUMMARY OF THE INVENTION
In view of the shortcomings of the prior art described above, it is an object of the present invention to provide a zoom lens system capable of compensating an introversive coma at a telephoto position where an off-axis aberration is compensated.
To achieve this object and in accordance with the purpose of the invention, the zoom lens system comprises;
a first lens group of a positive refractive power that moves linearly toward an object when changing a magnification;
a second lens group of a negative refractive power which is fixed against the image plane;
a third lens group of a positive refractive power that moves nonlinearly toward the object when changing a magnification; and
a fourth lens group of a negative refractive power that moves linearly toward the object when changing a magnification.
The zoom lens system according to the present invention also satisfies following conditions:
0.3 x fws34 < 0.5 x fw 0.2x fi - < f2 0.4 x f1 where fw is a focal length of the zoom lens system at a wide angle position, f3,4 is an effective focal length of the third lens group and the fourth lens group,
f2 is a focal length of the second lens group, and fl is a focal length of the first lens group.
BRIEF DESCRIPTION OF THE DRAWINGS
The above object and features of the present invention will be apparent from the following description of the preferred embodiment with reference to the accompanying drawings.
FIG. 1A is a sectional view illustrating a lens group of a zoom lens system at a wide angle position in accordance with a preferred embodiment of the present invention;
FIG. 1B is a sectional view illustrating a lens group of a zoom lens system at a normal position in accordance with a preferred embodiment of the present invention;
FIG. 1C is a sectional view illustrating a lens group of a zoom lens system at a telephoto position in accordance with a preferred embodiment of the present invention;
FIG. 2A is a view illustrating aberrations of the zoom lens system at a wide angle position in accordance with a first preferred embodiment of the present invention;
FIG. 2B is a view illustrating aberrations of the zoom lens system at a normal position in accordance with the first preferred embodiment of the present invention;
FIG. 2C is a view illustrating aberrations of the zoom lens system at a telephoto position in accordance with the first preferred embodiment of the present invention;
FIG. 3A is a view illustrating aberrations of the zoom lens system at a wide angle position in accordance with a second preferred embodiment of the present invention;
FIG. 3B is a view illustrating aberrations of the zoom lens system at a normal position in accordance with the second preferred embodiment of the present invention; and
FIG. 3C is a view illustrating aberrations of the zoom lens system at a telephoto position in accordance with the second preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
Referring to Figs. 1A-1C, a zoom lens system in accordance with the preferred embodiment of the present invention includes counting from the object side,
a first lens group 1 of a positive refractive power having two lenses which is linearly movable toward an object for a magnification change,
a second lens group 2 of a negative refractive power having three lenses which is fixed against the image plane,
a third lens group 3 of a positive refractive power having four lenses which is non-linearly movable toward the object for a magnification change, and
a fourth lens group 4 of a negative refractive power having three lenses which is linearly movable toward an object for a magnification change.
The first lens group 1 has one concave lens 15 which is concave toward an image plane, and one convex lens 16 cemented thereto. The second lens group 2 has a first lens 21 of a negative refractive power which is concave toward an image plane, a second lens 22 of a positive refractive power which is concave toward an image plane and is cemented to the first lens 21, and a third lens 23 of a negative refractive power which is concave toward an object. So, because the second lens group 2 has a negative refractive power, the light received is diverged. Therefore, the second lens group 2 compensates an introversive coma.
The third lens group 3 has two double convex lenses 35, 36 and one meniscus lens 37 which is concave toward an object, and one convex lens 38.
The fourth lens group 4 has a double convex lens 45 and two meniscus lenses 46, 47, one of which is cemented to the double convex lens.
To change the magnification, the first lens group 1 moves linearly toward an object and a second lens group 2 is fixed against an image plane. The third lens group 3 moves non-linearly toward the object as the first lens group 1 moves, and the fourth lens group 4 moves linearly toward the object according to the third lens group 3.
The first lens group 1 is composed of two lenses, converges the light entering from the object side. The light refracted by the first lens group 1 enters the second lens group 2 having three lenses, and finally diverges. The first lens 21 of a negative refractive power and the second lens 22 of a positive refractive power of the second lens group 2 correct an introversive coma caused by the axis aberration to improve the quality of the image.
The third lens group 3 has four lenses, and converges the light received from the second lens group 2. The fourth lens group 4 has three lenses, and diverges the light received from the third lens group 3. In addition, the zoom lens system in accordance with the first and second preferred embodiments of the present invention satisfies the following conditions:
0.3 x fw < f3,4: < 0.5 X fw ---------------- (1)
0.2 x fl < If21 < 0.4 x fl (2) where fw is a focal length of the zoom lens system at a wide angle position, f3,4 is an effective focal length of the third lens group and the fourth lens group, f2 is a focal length of the second lens group, and fi is a focal length of the first lens group.
Condition 1 focuses on the minimization of the total length of the zoom lens system. That is, condition 1 defines an optimum range of the focal length of the third lens group 3.
When the effective focal length f3,4 of the third lens group 3 and the fourth lens group 4 exceeds the upper limit in condition 1, the focal length f3 of the third lens group 3 becomes long. The longer focal length results in a longer distance between two conjugate points of the third lens group 3, which causes the total length of the zoom lens system to be long. On the other hand, when the effective focal length f3,4 of the third lens group 3 and the fourth lens group 4 is below the lower limits in condition 1, a focal length f3 of the third lens group 3 becomes too short. A too-short focal length f3 of the third lens group 3 makes it difficult to compensate all the aberrations such as spherical aberration.
When the absolute value If21 of the focal length f2 of the second lens group 2 is below the lower limit in condition 2, it is difficult to decrease the influence of the divergent power of the second lens group 2 while keeping the zoom lens size compact. On the other hand, when the absolute value If21 exceeds the upper limit in condition 2, lenses with large aperture sizes are needed to compensate the decreased amount of oblique ray.
The data according to the first preferred embodiment of the present invention is shown in Table 1. In accordance with the first preferred embodiment, the F number ranges from 4 to 5.8, and the focal length ranges from 71.5mm to 201.7mm. In the tables, r represents a radius of curvature, d represents a distance between lenses or thickness of a lens, nd represents a refractive power for d-line, and v represents an Abbe number of a lens. In each of these Tables, all units of length are denominated in millimeters.
Table 1
Surface Radius of Distance(di) Refractive Abbe No. Curvature(ri) Power(nd) Number (v) 1 82.78000 1.5000 1.80518 25.46 2 43.93800 5.2800 1.65844 50.85 3 -337.05300 A 4 1422.87600 1.0000 1.63854 55.45 5 19.63200 3.7200 1.80518 25.46 6 47.09200 2.5800 7 47.36700 1.0000 1.77250 49.62 8 113.79500 B 9 87.85700 3.2700 1.48749 70.44 10 -60.00000 0.1500 11 47.37000 4.4800 1.51680 64.20 12 47.54400 1.0000 1.80518 25.46 13 833.76900 0.1500 14 38.80300 2.7800 1.48749 70.44 15 336.35900 1.5000 16 0.00000 C 17 0.00000 12.4500 18 71.42000 3.6900 1.64769 33.84 19 -33.15400 1.1000 1.63854 55.45 20 -126.31300 2.2900 21 -24.18600 1.1000 1.77250 49.62 22 -141.40300 A, B, and C represent variable distances between surfaces in accordance with the wide angle position, the normal position, and the telephoto position, as shown in Table 2. Bf represents a back focal length.
Table 2
Focal Wide Angle Normal Telephoto Lengi(f) Position(f=71.5) Position(f=109.0) Position(f=201.7) A 1.251 20.396 39.663 B 20.673 13.758 1.282 C 18.998 18.234 19.005 Bf 37.496 45.175 56.880
f3,4 T 31.15 31.37 31.15 The focal length fi of the first lens group 1 according to the first preferred embodiment of the present invention is 120.31mm, the focal length f2 of the second lens group 2 according to the first preferred embodiment of the present invention is -32.19mm.
The data according to the second preferred embodiment of the present invention is shown in Table 3. In accordance with the second preferred embodiment of the present invention, the F number ranges from 4 to 5.8, and the focal length ranges from 71.3mm to 201.8mm.
Table 3
Surface Radius of Distance(di) Refractive Abbe No. Curvature(ri) Power(nd) Number (v) 1 81.87800 1.6000 1.80518 25.46 2 43.44200 5.6300 1.65844 50.85 3 -336.23900 A 4 -321.81100 1.2000 1.63854 55.45 5 19.95200 3.4300 1.80518 25.46 6 53.67000 2.1100 7 -5298800 1.0000 1.77250 49.62 8 97.11000 B 9 71.99500 32600 1.51155 67.67 10 -71.99500 0.1500 11 47.30900 4.5000 1.51680 64.20 12 47.30900 1.1000 1.83606 24.25 13 6110.30800 0.1500 14 44.90200 2.6000 1.51680 64.20 15 0 509.90600 1.4300 16 0.00000 C 17 0.00000 12.4500 18 66.81200 3.4300 1.64769 33.84 19 -37.44700 1.1000 1.63854 55.45
20 -160.95500 2.5000 21 -24.35300 1.1000 1.77250 49.62 22 -134.81100 A, B, and C represent variable distances between surfaces in accordance with the wide angle position, the normal position, and the telephoto position, as shown in Table 4. Bf represents a back focal length.
Table 4
Focal Wide Angle Normal Telephoto Len Position f=71.3 Position f=108.8 Position f=201.8 A 1.593 20.657 39.794 B 20.673 13.760 1.282 C C 18.998 18.234 19.006 Bf 37.505 45.182 56.888 f3,4 31.06 31.28 31.06 The focal length fi of the first lens group 1 according to the second preferred embodiment of the present invention is 119.28mm, the focal length f2 of the second lens group 2 according to the second preferred embodiment of the present invention is -32.19mm.
As described above, the effect of the zoom lens system in accordance with the preferred embodiment of the present invention lies in that it is able to obtain good image quality because coma is corrected at the telephoto position.
Moreover, the ratio of the intensity of the surrounding radiation becomes high.
While it has been shown and described the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications can be readily made therein without departing from the scope and spirit of the invention as defined by the appended claims.
Claims (4)
1. A zoom lens system comprising when viewed from an object side:
a first lens group of a positive refractive power which moves linearly toward the object for a magnification change;
a second lens group of a negative refractive power which is fixed;
a third lens group of a positive refractive power which moves nonlinearly toward the object for a magnification change; and
a fourth lens group of a negative refractive power which moves linearly toward the object for a magnification change,
wherein 0.3 x fw#f3,4#0.5 x fw 0.2x fl s If21 s 0.4 x f1 where fw is a focal length of the zoom lens system at a wide angle position,
f3,4 iS an effective focal length of the third lens group and the fourth lens group, f2 is a focal length of the second lens group, and fl is a focal length of the first lens group.
2. A zoom lens system according to claim 1, wherein the first lens group
includes a convex lens and a concave lens cemented thereto.
3. A zoom lens system according to claim 1, wherein the second lens group includes at least a concave lens and a meniscus lens cemented thereto.
4. A zoom lens system substantially as hereinbefore described with reference to and as shown in Figures 1A to 2C; or Figures 3A to 3C of the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1019960078434A KR19980059098A (en) | 1996-12-30 | 1996-12-30 | Zoom lens |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9726466D0 GB9726466D0 (en) | 1998-02-11 |
| GB2320767A true GB2320767A (en) | 1998-07-01 |
| GB2320767B GB2320767B (en) | 1999-04-14 |
Family
ID=19492868
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9726466A Expired - Fee Related GB2320767B (en) | 1996-12-30 | 1997-12-15 | Four group zoom lens system |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5903398A (en) |
| JP (1) | JP3122404B2 (en) |
| KR (1) | KR19980059098A (en) |
| CA (1) | CA2225969C (en) |
| GB (1) | GB2320767B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004184526A (en) * | 2002-11-29 | 2004-07-02 | Pentax Corp | Zoom lens system |
| JP4936437B2 (en) * | 2006-09-19 | 2012-05-23 | オリンパスイメージング株式会社 | Zoom lens and electronic imaging apparatus using the same |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4701033A (en) * | 1983-09-09 | 1987-10-20 | Minolta Camera Kabushiki Kaisha | Variable focal length lens system |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5528427A (en) * | 1991-10-30 | 1996-06-18 | Canon Kabushiki Kaisha | Zoom lens |
| US5815320A (en) * | 1993-01-14 | 1998-09-29 | Canon Kabushiki Kaisha | Zoom lens |
| JP3395169B2 (en) * | 1993-05-31 | 2003-04-07 | 株式会社ニコン | Zoom lens with anti-vibration function |
| JPH0772390A (en) * | 1993-09-02 | 1995-03-17 | Nikon Corp | Small zoom lens |
| JPH07199070A (en) * | 1993-12-28 | 1995-08-04 | Nikon Corp | Zoom lens |
-
1996
- 1996-12-30 KR KR1019960078434A patent/KR19980059098A/en not_active Ceased
-
1997
- 1997-12-15 GB GB9726466A patent/GB2320767B/en not_active Expired - Fee Related
- 1997-12-22 US US08/996,289 patent/US5903398A/en not_active Expired - Lifetime
- 1997-12-24 CA CA002225969A patent/CA2225969C/en not_active Expired - Fee Related
- 1997-12-25 JP JP09357326A patent/JP3122404B2/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4701033A (en) * | 1983-09-09 | 1987-10-20 | Minolta Camera Kabushiki Kaisha | Variable focal length lens system |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9726466D0 (en) | 1998-02-11 |
| KR19980059098A (en) | 1998-10-07 |
| US5903398A (en) | 1999-05-11 |
| JP3122404B2 (en) | 2001-01-09 |
| CA2225969C (en) | 2001-05-08 |
| JPH10197795A (en) | 1998-07-31 |
| CA2225969A1 (en) | 1998-06-30 |
| GB2320767B (en) | 1999-04-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) |
Free format text: REGISTERED BETWEEN 20090813 AND 20090819 |
|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) |
Free format text: REGISTERED BETWEEN 20101209 AND 20101215 |
|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20161215 |